The contribution of splanchnic and extrasplanchic tissues to the blood metabolic clearance rate (MCR) of progesterone will continue to be studied. The uterine estraction and conversion of progesterone to 20 alpha-hydroxypregn-4-en-3-one and 5 alpha-pregnan-3, 20-dione will be studied in women during the follicular and luteal phase of the menstrual cycle. The uterine extraction and transuterine interconversion of estradiol and estrone will also be measured in these same women. The MCR and splanchnic, extrasplanchnic and kidney clearance of progesterone will be determined in monkeys. The effect of increasing the production rate of cortisol on the MCR of progesterone will be studied in women during the follicular and luteal phase of the menstrual cycle. This will be compared with the MCR of progesterone in pregnant women immediately before and during active labor. The interrelationship of progesterone extraction and metabolism by the rabbit uterus in vivo and uteroglobin content of the uterine lumen is also being studied.